Devices for infusing to a patient a beneficial agent such as a drug diffused in a medical liquid are known in the art. The most common type of such device utilizes an elevated glass or flexible container having the beneficial agent diffused in a medical liquid which is fed by gravity to a patient's venous system via a length of flexible plastic tubing and a catheter. The rate of flow in this type of device is commonly regulated by an adjustable clamp on the tubing. This type of infusion suffers from the drawback of requiring a relatively stationary patient and is dependent on the height differential between the source of liquid and the patient for accurate delivery rates.
Another type of infusion device utilizes electromechanical components in a pump to provide fluid propulsion of the liquid for infusion into the patient. Such electronically controlled infusion devices, however, suffer from several drawbacks including the cost of such electrical components as well as the limit such electrical components and the necessary power source place on the size and thus portability of the device.
Devices in the art are also utilized which employ an elastomeric bladder which contains the liquid to be infused under pressure for infusion. Such elastomeric bladder infusion devices are seen in Winchell et al. U.S. Pat. No. 4,741,733 and Hessel U.S. Pat. No. 4,769,008, both of which are assigned to the assignee of the present invention.
While elastomeric bladder infusion devices such as seen in the Hessel and Winchell et al. patents provide an accurate flow of the liquid being infused over an extended period of time, the amount of liquid to be infused is limited by the size of the devices. While simply utilizing a larger bladder and a resultant larger housing would provide more liquid to be infused, such devices would be exceedingly large. Additionally, if the liquid to be infused is stored in a frozen state, an excessive amount of time would be required to thaw the liquid prior to dispensing because of the small surface area of the liquid.
What would thus be desirable would be an infusion device capable of containing a large amount of liquid to be infused which would not be exceedingly large to carry. Additionally, the infusor should store the liquid to be infused in a manner which, when frozen, is easy to thaw. Finally, such device should not be cost prohibitive. The present invention meets these requirements.